The difference in the population density of pill bugs in the Metro Vancouver area


  • Ahsan Khan
  • Andrew Lee
  • Edmund Kwan
  • Parham Asli


The differences in the population density of pill bugs between two different locations in
Metro Vancouver were studied to determine if there was a difference between the locations. The
significance of studying pill bugs is due to the fact that they are quite essential to nutrient cycling
since they help remove harmful metals from the soil. The population density was measured in
November from the 9th to 18th and was calculated using Chapman's estimator, a capturerecapture
method to obtain an unbiased estimated population size. The experiment assumed
that the population was static without immigration or migration occurring. Pill bugs were marked
two days before their recapture and the captured pill bugs were recorded along with the
temperature. After two days, the sites were revisited to count the total number of marked and
unmarked pill bugs. As for statistical analysis, the temperature was recorded but returned a
value of r=0.022599 which supported that temperature does influence population density. As for
the difference between the North Shore area and UBC area, with the r-value obtained above, it
was concluded that there is no difference in population density between the two areas as the pvalue
obtained was p=0.966108. This did not provide sufficient evidence to reject the null
hypothesis which led to the conclusion that the difference was due to chance.